Re: [Qemu-devel] [PATCH] w32: Fix build with older gcc (unresolved symbol)

[Igor Mitsyanko <i.mitsyanko@gmail.com>]

On 29.03.2013 21:20, Stefan Weil wrote:
> The cross i586-mingw32msvc-gcc 4.4.4 from Debian Squeeze does not support
> __sync_val_compare_and_swap by default.
>
> Using -march=i686 fixes that and should also result in better code.
>
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> ---
>
> Maybe this modification is also needed for native gcc-4.4 and older
> on Linux i386. If yes, we can move the new script code out of the
> MinGW conditional code.
>
> Newer versions of gcc obviously use -march=i686 by default and
> don't need the patch, but it also won't do any harm for those
> versions.
>
> Stefan
>

mingw is built with --build=mingw32 and looks like it defaults to 
-march=i386 (I have gcc version 4.7.2).
Default build on windows is broken without this patch, it should be
applied to 1.5 probably.

Tested-by: Igor Mitsyanko <i.mitsyanko@gmail.com>

>
>   configure |    5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/configure b/configure
> index f2af714..70c2219 100755
> --- a/configure
> +++ b/configure
> @@ -562,6 +562,11 @@ if test "$mingw32" = "yes" ; then
>     QEMU_CFLAGS="-DWIN32_LEAN_AND_MEAN -DWINVER=0x501 $QEMU_CFLAGS"
>     # enable C99/POSIX format strings (needs mingw32-runtime 3.15 or later)
>     QEMU_CFLAGS="-D__USE_MINGW_ANSI_STDIO=1 $QEMU_CFLAGS"
> +  if test "$cpu" = "i386"; then
> +    # We need something better than i386 for __sync_val_compare_and_swap
> +    # and can expect that QEMU will only run on i686 or later.
> +    QEMU_CFLAGS="-march=i686 $QEMU_CFLAGS"
> +  fi
>     LIBS="-lwinmm -lws2_32 -liphlpapi $LIBS"
>   cat > $TMPC << EOF
>   int main(void) { return 0; }
>